1. Field of the Invention
The present invention relates to a lighting or illumination assembly and system. More particularly, the present invention relates to a high coupling efficiency illumination system including a plurality of light sources.
2. Background Art
Illumination systems are used in a variety of applications. Home, medical, dental, and industrial applications often require light to be made available. Similarly, aircraft, marine, and automotive applications require high-intensity illumination beams.
Traditional lighting systems have used electrically powered filament or arc lamps, which sometimes include focusing lenses and/or reflective surfaces to direct the produced illumination into a beam. However, in certain applications, such as in swimming pool lighting, the final light output may be required to be placed in environments in which electrical contacts are undesirable. In other applications, such as automobile headlights, there exists a desire to move the light source from exposed, damage-prone positions to more secure locations. Additionally, in yet other applications, limitations in physical space, accessibility, or design considerations may require that the light source be placed in a location different from where the final illumination is required.
In response to some of these needs, illumination systems have been developed using optical waveguides to guide the light from a light source to a desired illumination point. One current approach is to use either a bright single light source or a cluster of light sources grouped closely together to form a single illumination source. The light emitted by such a source is directed with the aide of focusing optics into a single optical waveguide, such as a large core plastic optical fiber, that transmits the light to a location that is remote from the source/sources. In yet another approach, the single fiber may be replaced by a bundle of individual optical fibers.
The present methods are very inefficient with approximately 70% loss of the light generated in some cases. In multiple fiber systems, these losses may be due to the dark interstitial spaces between fibers in a bundle and the efficiencies of directing the light into the fiber bundle. In single fiber systems, a single fiber having a large enough diameter to capture the amount of light needed for bright lighting applications becomes too thick and loses the flexibility to be routed and bent in small radii.
Some light generating systems have used lasers as sources, to take advantage of their coherent light output and/or low divergence angle. However, laser sources typically produce a single wavelength output color whereas an illumination system typically requires a more broadband white light source. For example, U.S. Pat. No. 5,299,222 discusses the use of single wavelength high-power laser diodes to couple energy into a wavelength sensitive gain medium, as opposed to use as an illumination source. The use of the specified laser diodes, with their asymmetrical beam shape, requires the extensive use of optical beam shaping elements in order to achieve more efficient coupling into the optical fibers. Also, some laser diodes are expensive to utilize since they require stringent temperature control (e.g., the need for using thermoelectric coolers, and the like) due to the heat they generate in operation. In addition, a concentrated array of packaged LEDs can lead to problems in the area of thermal management.
The need remains for a lighting system that can deliver high-intensity illumination using a light source.